Fracture-induced thermal decomposition in brittle crystalline solids

Abstract

An experimental study has been made of the thermal decomposition produced by the release of elastic strain energy when a fast cleavage crack runs through a brittle crystalline solid. The amounts of decomposition are measured for cleavages in crystals of calcium, magnesium, and lead carbonates and sodium and lead azides. By relating these amounts to the fracture velocity and the kinetics of thermal decomposition of each material measured independently, a figure for the crack tip temperature is deduced in each case. The significance of this temperature and its relevance to the possibility of generating fast self-sustaining reactions in solids are discussed. The relative magnitudes of the crack temperatures can be semi-quantitatively related to the plastic properties of the material as deduced from measurements of their indentation hardness on the cleavage plane. Finally the decomposition of a more complex molecule by this method is illustrated for the case of the organic compound pentaerythritol tetranitrate. ‘Hence, rupture should be accompanied by phenomena such as a large rise in temperature indicative of the dissipation of an amount of energy... ’ A. A. Griffith (1920)